Electrochemical Determination of Sulfide at High Temperatures via Its Electrochemically Initiated Reaction with Diethyl‐p‐phenylenediamine in Dimethylformamide

The electrochemical oxidation of DEPD proceeds via an EC_revECE mechanism in dimethylformamide. It has been investigated at elevated temperatures up to 130 °C at both micro and macro platinum and glassy carbon electrodes. Kinetic and thermodynamic parameters for the reaction process have been calculated for each temperature. Further, the voltammetric response of DEPD shows enhanced limiting currents in the presence of sulfide. The analytical utility of the approach has been investigated with linear range from 50 to 850 μM sulfide concentration observed and a corresponding limit of detection of 20 μM achievable at temperatures of 70 °C.     

KoBra: A rate constant method for prediction of the diffusion of sorbates inside nanoporous materials at different loadings

We present a new method for calculating the diffusion tensor for the systems of sorbates inside nanoporous materials at different loadings by just using transition rate constants. In addition, a user-friendly program with graphical user interface has been developed and is freely provided to be used ( https://sourceforge.net/projects/kobra/ ). It needs from the user just to provide the values of the unit cell lengths and angles, the transition rate constants for each sorbate, and any spatial constraint between these sorbates. This program is shown to be about 30 times faster than kinetic Monte Carlo method. Application of the method to the problem of diffusion of aromatics in silicalite-1 at different loadings is presented too. © 2019 Wiley Periodicals, Inc.     

无源LC传感器信号读取系统扫频源设计

针对连续快速的高频线性扫频信号源在无源LC传感器信号读取中的应用需求,设计并实现了0～400MHz任意频率段的线性扫频源系统。该系统的核心器件为直接数字频率合成器(DDS)AD9910,采用该芯片的RAM模式和数字斜坡模式,详细介绍各模式工作原理及寄存器的具体配置过程,并分别以这两种模式实现了输出扫频信号。测试结果表明,两种方式均可实现高频高速捷变稳定信号的连续扫频。该扫频源具有高精度、稳定性好、频率捷变快和小型化的等特,为LC传感器的工程应用提供技术基础。     

Theoretical and Experimental Study of the Homogeneous Catalytic Oxidation of Nicotinamide Adenine Dinucleotide (NADH) at Spherical Gold Electrodes Using Linear Sweep Voltammetry and Chronopotentiometry

The homogeneous catalytic oxidation of coenzyme nicotinamide adenine dinucleotide (NADH) with dopamine at a thiolactic acid modified gold spherical electrode of radius 0.0128 cm has been studied in aqueous phosphate media (pH 7.0) using linear sweep voltammetry and chronopotentiometry with power time and exponential time currents. We have proved that, under the conditions of this study, the steady state is reached, in such a way that the expressions for the I?E and dI/dE?E responses are simplified and become independent of time and the electrochemical technique employed. Therefore, the experimental I?E and dI/dE?E curves obtained in chronopotentiometry and linear sweep voltammetry are practically superimposable and, from easy expressions for the peak parameters of the dI/dE?E curves deduced in this paper, values of the chemical and electrochemical rate constants have been obtained.     

紫草素的电化学伏安行为研究

紫草素在0.2 mol/L HAc-NaAc缓冲溶液(pH4.3)中,产生灵敏的线性扫描极谱峰,峰电位EP=-0.186 V(vs.Ag/AgCl)。峰电流与紫草素浓度在5×10-7~1×10-5mol/L范围内呈良好的线性关系。可用于紫草中紫草素含量的测定。用线性扫描和循环伏安法测试表明,该体系属具有反应物吸附性的可逆过程体系。     

头孢噻肟钠的极谱伏安行为及其单扫描示波极谱法测定

以多种电化学手段研究了头孢噻肟钠的极谱伏安行为，在磷酸盐缓冲溶液中，头孢噻肟钠产生了一个不可逆吸附不原波，其峰电位为－０．７７Ｖ（ｖｓ．ＳＣＥ）。有二个电子和一个质子参与了电极反应。电极反应速率常数Ｋｓ为９．０×１０＾－６ｃｍ．ｓ＾－１。     

Electrochemical reduction of cefminox at the mercury electrode and its voltammetric determination in urine

The electrochemical behaviour of cefminox in phosphate buffers solutions over pH range 2.0-9.0 using differential-pulse polarography, DC-tast polarography, cyclic voltammetry and linear sweep voltammetry (staircase) has been studied. In acidic media, a non reversible diffusion-controlled reduction involving two electrons occurs and the mechanism for the reduction was suggested. A differential-pulse polarographic method for the determination of cefminox in the concentration range 5.8×10⁻⁶-6.0×10⁻⁵ M with a detection limit of 1.76×10⁻⁶ M was proposed. Also, a method based on controlled adsorptive pre-concentration of cefminox on the hanging mercury drop electrode followed by linear sweep voltammetry, allows its determination in the concentration range 8.3×10⁻⁸-1.5×10⁻⁶ M with a detection limit of 2.47×10⁻⁸ M. These methods have been used for the direct determination of cefminox in human urine with recoveries between 98 and 103%, and precision around ±2%.     

孕血和药物中孕酮的单扫极谱法测定

孕酮２，４－二硝基苯腙在单扫描示波极谱仪上，以吡啶－氢氧化钠为底液（ｐＨ２．０）于－０．７４Ｖ（ｖｓ．ＳＣＥ）处可出现一灵敏的吸附催化波，孕酮浓度在１．０×１０＾－８～２．０×１０＾－６ｍｏｌ／Ｌ范围内与该波呈线性关系，检出限为５．０×１０＾－９ｍｏｌ／Ｌ方法用于测定孕血和药物中孕酮含量，获得满意的结果。     

舒乐安定在铂离子注入修饰电极上的电化学行为及其应用

舒乐安定在0.1 mol/L NH3-NH4Cl缓冲溶液(pH 9.40)中,用线性扫描伏安法,在Pt/GC离子注入修饰电极上,形成一良好的线性扫描伏安还原峰,峰电位Ep=-0.70V(vs.SCE)。其峰电流与舒乐安定浓度在3.0×10-9-1×107和1×10-7-1.5×10-6mol/L范围内呈线性关系,相关系数均为0.9999,检出限为3.0×10-9mol/L。并用于片剂的测定,回收率在96.5％～98.5％之间,结果是可靠的。用循环伏安法研究了体系的性质。实验表明,电极过程为不可逆吸附。用AES、XPS和SEM等表面分析方法证明,Pt离子确实注入到玻碳基体电极表面,Pt以原子态存在,催化了舒乐安定的还原。     

Rapid determination of telmisartan in pharmaceuticals and serum by the parallel catalytic hydrogen wave method

The polarographic characteristics of telmisartan have been investigated in 0.8 mol L^–1 NH₃.H₂O–NH₄Cl (pH 8.9)–0.01 mol L^–1 H₂O₂ as supporting electrolyte. The results demonstrate that the polarographic reduction wave at ca. –1.30 V in the absence of H₂O₂ is a catalytic hydrogen wave, and the reduction wave enhanced by H₂O₂ is a so-called parallel catalytic hydrogen wave. The analytical sensitivity of the parallel catalytic hydrogen wave is ca. 60 times higher than that of the corresponding catalytic hydrogen wave. Based on the parallel catalytic hydrogen wave a novel method has been developed for determination of telmisartan by linear sweep polarography. The calibration curve is linear in the range 2.0×10^–8–2.0×10^–6 mol L^–1 and the detection limit is 1.0×10^–8 mol L^–1. The precision is excellent with relative standard deviations of 2.6% at a concentration of 1.0×10^–7 mol L^–1 telmisartan. The proposed method has been applied to the direct determination of the telmisartan in capsule forms and biological samples. The proposed method has been proved to be advantageous over existing CZE and MEKC methods in simplicity, rapidity, and reproducibility.